kilovatt

Kilovatt (symbol kW) is a unit of power in the International System of Units (SI). It denotes 1000 watts, where a watt is defined as one joule per second. The kilowatt is used to express the output or input power of machines, electrical devices, and systems.

Kilowatts are commonly used for larger electrical and mechanical power ratings. Examples include air conditioners, electric heaters, motors, and solar photovoltaic arrays. In automotive and industrial contexts, engines and equipment are often rated in kilowatts to indicate maximum useful power. In general, 1 kW is roughly equivalent to 1.34 horsepower (mechanical hp).

Power versus energy is an important distinction: kilowatts measure rate (power), while kilowatt-hours measure energy. Household electricity usage is billed in kilowatt-hours, which represent the amount of energy consumed over time. A device rated at 1 kW, running for one hour, would consume 1 kWh of energy. The same device running for two hours would consume 2 kWh.

The name kilowatt reflects its prefix meaning of thousand (kilo) and the unit watt, named after James Watt. The kilowatt is widely used because it provides a practical scale for human-made systems, from small appliances to utility-scale power generation. Understanding kilowatts helps in comparing device capabilities, planning electrical installations, and estimating energy costs.